请安装mysql2适配器

Question

gem 'rails', '3.2.9'
# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'
#gem 'sqlite3'
# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails',   '~> 3.2.3'
#  gem 'coffee-rails', '~> 3.2.1'
  # See https://github.com/sstephenson/execjs#readme for more supported runtimes
  # gem 'therubyracer', :platforms => :ruby
 # gem 'uglifier', '>= 1.0.3'
end
 gem 'coffee-rails', '~> 3.2.1'
 gem 'uglifier', '>= 1.0.3'
gem 'jquery-rails'
# To use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.0.0'
# To use Jbuilder templates for JSON
# gem 'jbuilder'
# Use unicorn as the app server
# gem 'unicorn'
# Deploy with Capistrano
# gem 'capistrano'
# To use debugger
# gem 'debugger'
# this gems needs for auth
gem 'cancan'
gem 'devise'
gem 'rolify'
gem 'execjs'
gem 'therubyracer', :platform => :ruby
gem 'populator'
gem 'faker'
gem 'paperclip'
gem 'simple_xlsx_writer'
gem 'roo'
gem 'mysql2', '0.3.11'
gem 'simple_xlsx_writer'
gem 'rake', '~> 10.0.4'
gem 'icalendar'

development:

  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: emc
  pool: 5
  username: root
  password: root
  socket: /var/run/mysqld/mysqld.sock
testing:

  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: emc
  pool: 5
  username: root
  password: root
  socket: /var/run/mysqld/mysqld.sock
production:

  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: emc
  pool: 5
  username: root
  password: root
  socket: /var/run/mysqld/mysqld.sock

警告：此版本的mysql2(0.2.18)与Rails 3.1不兼容，因为ActiveRecord适配器已拉入Rails本身。
警告：如果您打算在Rails中使用0.3.x（或更高版本），请使用它>=3.1.x
rake aborted！
未定义方法`accept'for nil:nilclass
任务:TOP=>db:migrate
（通过运行任务查看完整跟踪）**

希望有人能帮助我，谢谢。

Answer 1

试着给你gemfile

而不是使用：

gem 'mysql2', '0.3.11'

使用此：

gem 'mysql2'

gem 'simple_xlsx_writer'